At present, remote remote electric quantity collection meter remote electric quantity collection reading and remote control system has attracted more and more attention OMRON in OMRON the OMRON power sector. The use of Modem and computer, the use of public telephone network for remote control, not only can be very convenient to achieve control of the transmission of information, and the control of information can be very complex and rich. But the system cost is high, and the structure is complex. This design uses the PLC to realize the power supply system's electric quantity collection and the control, through the public telephone network and the upper computer is connected. The whole system has flexible control, reliable operation, low cost and wide application prospect.
2, system structure
This design uses electric quantity timing acquisition, according to the user's requirements for data acquisition and recording time. The electric quantity signals are transformed into a pulse signal by the pulse electric meter, and the electric quantity is directly proportional to the relationship. Assuming that every day is divided into 7 periods of data collection, the road every day to record 16 words, that is: mark and year 1 words, month, day 1 words, time, a total of 14 groups of 7 words. The data stored in the DM, if each cycle by a month, the need to use memory 16 x 500 about 31 words.Data in DM, read by the host computer time.
The key to this system is to store a large amount of data, and to have the ability to communicate. PLC speaking, only a small amount of input points, not the output point, but there should be a system clock. CQM1 series PLC with a communication port, and the DM area is larger, can be configured with the system clock memory cell. The specific configuration of the design is as follows:
CPU:CQM1-CPU41 (comes with $point input module), and with RS-232 interface;
Memory: CQM1-ME04R, can save 4K user program, with the system clock;
Power supply: CQM1-PA206, AC power supply, and provide 24V DC power supply, the use of the input point;
Through the MODEM and public telephone network can realize the power of any distance measurement.
3, data collection
In this system, the timing acquisition method is used to record the actual power value according to the time period, and the data is stored in the DM data area. Specific process is:
Set the A17 for real-time clock, representative, and compared with 1000, to determine whether the 10 points to 00 points, if that is equal to ON, at the same time to collect channel of the contents stored in the DM area, after being a pointer plus 1, and then judge whether the pointer beyond the data range. If not, not what to do; if, while 0000 re assigned to the pointer, even if its from the storage area at the beginning of the number, start the next cycle.
This design, in order to ensure the power acquisition accuracy, without losing the pulse, to take a regular approach to the implementation of the acquisition subroutine, every 10ms acquisition. As a result of the use of timing acquisition, the number of fixed format, and the length of the storage area and the length of the number of coordination, in the number of storage at the same time, can not save time. Because from the pointer value can know the current number of storage to what position, and the different location of the data, and represent the number of different moments, the regularity is obvious, it is easy to figure out the time of the data storage.
4, remote control
In order to save investment and improve the control efficiency, remote control method can be adopted. CQM1 machine through the appropriate configuration, can be easily realized remote control, but does not increase the total number of I/O can be controlled.
The interface unit is connected with an input or output terminal, and the maximum distance can reach 500m ".
The maximum transmission distance of the control mode is 500m, but the actual distance is related to the transmission delay and power distribution mode. The main part of the CQM1 is connected with the B7A interface unit, and the corresponding terminal is connected at a distance. Connection between the terminal and the interface by twisted pair.
The structure of the interface unit is similar to the I/O module of CQM1, and can be used in the same way as the I/O module, which is connected to the CQM1 main system. The interface unit is divided into two types: the input terminal and the output terminal, and the terminal input and output are divided into two categories.In this way, a PLC can be connected to the 64-96 meter.
5 Data display
In addition to using the monitoring and recording of the host computer, the seven segment decoding method can be used to monitor the power supply situation. In this design, the power data is directly output to the seven segment decoder by the output unit, and the output value is displayed after decoding.
A number of 4 points, the use of OMRON dynamic output unit (a unit can be output 128 points), the external hardware decoding as a latch mode, the unit can be a stable display of 32 digits.
In this design, the PLC system uses pulse counting, analog unit is not used, so that the anti-interference ability of the system is greatly improved. In addition, the data acquisition process, the contents of the A17 stored in the modified pointer to point to the DM word, and then modify, and then determine the control pointer. Not only A17, but also the year, month, day, and some of the signs are pre stored, the same way to save a few.
The system has been proved by simulation research and practical application. The system is reliable and accurate.